The formation of tunnel junctions for applications in amorphous silicon (a-Si:H) based multijunction n-i-p solar cells has been studied using real time optics. The junction structure investigated in detail here consists of a thin ({approximately} 200 {angstrom}) layer of n-type microcrystalline silicon ({micro}c-Si:H) on top of an equally thin layer of p-type {micro}c-Si:H, the latter deposited on thick ({approximately} 2,000 {angstrom}) intrinsic a-Si:H. Such a structure has been optimized in an attempt to obtain single-phase {micro}c-Si:H with a high crystallite packing density and large grain size for both layers of the tunnel junction. They have explored the conditions under whichmore » grain growth is continuous across the p/n junction and conditions under which renucleation of n-layer grains can be ensured at the junction. one important finding of this study is that the optimum conditions for single-phase, high-density {micro}c-Si:H n-layers are different depending on whether the substrate is a {micro}c-Si:H p-layer or is a H{sub 2}-plasma treated or untreated a-Si:H i-layer. Thus, the top-most {micro}c-Si:H layer of the tunnel junction must be optimized in the multijunction device configuration, rather than in single cell configurations on a-Si:H i-layers. The observations are explained using an evolutionary phase diagram for a-Si:H and {micro}c-Si:H film growth versus thickness and H{sub 2}-dilution ratio, in which the boundary between the two phases is strongly substrate-dependent.« less

The reliability of hydrogenated amorphous silicon multijunction solar cells was investigated. The n/p interface is thought to play an important role in light-induced effect of multijunction solar cells. Blocking barriers which promote carrier recombination at n/p interface were applied here. As compared with ordinary solar cell, this solar cell shows an excellent stability for light exposure. The stability for thermal treatment is also discussed.

The role of the back reflector texture on the initial and stabilized efficiency of high efficiency triple-junction triple-bandgap amorphous silicon alloy based cells has been investigated. The devices have been deposited on Ag/ZnO back reflector possessing three different textures. The performance of the bottom single-junction a-SiGe alloy n i p cell on the three textures has also been analyzed. The value of the short-circuit current density of the n i p cell initially increases and then decreases with increasing texture. Light soaking results show that the higher textures exhibit superior device stability. Degradation as low as 8% has been obtainedmore » on the triple-junction cells.« less